PORTABLE VIDEO-ON-DEMAND IN WIRELESS COMMUNICATION

Our present ability to work with video has been confined to a wired en vironment, requiring both the video encoder and decoder to be physical ly connected to a power supply and a wired communication link. This pa per describes An integrated approach to the design of a portable video -on-demand system capable of delivering high-quality image and video d ata in a wireless communication environment. The discussion will focus on both the algorithm and circuit design techniques developed for imp lementing a low-power video compression/decompression system at power levels that are two orders of magnitude below existing solutions. This low-power video compression system not only provides a compression ef ficiency similar to industry standards, but also maintains a high degr ee of error tolerance to guard against transmission errors often encou ntered in wireless communication The required power reduction can best be attained through reformulating compression algorithms for energy c onservation. We developed an intra-frame compression algorithm that re quires minimal computation energy in its hardware implementations. Exa mples of algorithmic trade-offs are the development of a vector quanti zation scheme that allows on-chip computation to eliminate off-chip me mory accesses, the use fo channel-optimized delta representations to a void the error control hardware that would otherwise be necessary and the coding of internal data representations to further reduce the ener gy consumed in data exchanges, The architectural and circuit design te chniques used include the selection of a filter bank structure that mi nimizes the energy consumed in the datapath, the data shuffle strategy that results in reduced internal memory size, and the design of digit al and analog circuits optimized for low supply voltages, Our hardware prototype is a video decoding chip set for decompressing full-motion video transmitted through a wireless link at less than 10 mW, which is incorporated into a hand-held portable communication device with a co lor display. We will describe the design tradeoffs of the prototype fo r low-power purposes, and quantify the system's performance in both co mpression efficiency and power dissipation.